A large majority of the mothers with young children are now part of the work force, and thus these mothers are required to leave their children (some of whom are infants) with day care centers or else employ a live-in nanny or an au pair.
According to a nationally-projectable poll conducted by PARENTS MAGAZINE, almost seventy-five percent of families in the United States now use some form of child care; and many are unhappy with that care.
Moreover, there are reported cases where the child was exposed to a very undesirable environment or even subjected to abuse or violence. While these cases are in the minority or somewhat isolated, nevertheless they were indeed shocking and alarming; and as in other situations, the perception becomes the reality.
As a result, the parents are under stress and anxiety on the job and, of course, are worried about leaving their children in the temporary care of another about whom they often know very little (such as a stranger). This stress reduces job efficiency and production.
More recently, parents have installed hidden video cameras in an attempt to monitor in-home nannies or baby-sitters; these are stationary systems, not portable, and are expensive to install and to maintain.
Similar situations arise whenever an older person, geriatric or other patient, or even a pet, is left in the care of another or in a facility or institution (and either on a temporary basis or for an indefinite length of time).
In the prior art, attempts have been made to monitor child activity. For example, a commercially-available product basically consists of an FM transmitter attached to a baby's crib and transmitting a signal to a receiver close to the parent or parents elsewhere in the home.
Similarly, U.S. Pat. No. 5,119,072 issued in 1992 discloses a transmitter attached to a child's arm and having an antenna for broadcasting an FM RF signal. A receiver is carried by the parent or guardian; and when the amplitude of the carrier field strength is less than a predetermined threshold value, an alarm is sounded to indicate that the child is out of the desired range.
While these prior art solutions are interesting concepts and perhaps useful for the purposes intended, they are not completely satisfactory.